The food preservative potential of essential oils: is lemongrass the answer?

Several essential oils of medicinal plants possess proven antimicrobial activity and are suitable for applications on the food industry. The oil from Cymbopogon citratus (lemongrass) has been reported to have a wide range of biological activities. However, there are few controlled studies confirming its antimicrobial activity. The aim of our study was to assess the antimicrobial potential of lemongrass oil against a wide spectrum of food spoilage and pathogenic bacteria and yeast in liquid and vapour phase. The chemical composition of the oil was analyzed by gas chromatography; 14 components were identified and geranial (28.93 %), neral (24.30 %) and myrcene (23.92 %) were the most abundant constituents. Lemongrass oil showed potent antimicrobial activity against Gram positive bacteria and exhibited the strongest antifungal effect against Candida albicans and C. parapsilosis. Minimum inhibitory concentration varied from 0.019 to 1.25 mg mL^?1 for Gram positive bacteria and yeasts, indicating Staphylococcus aureus, S. epidermidis and C. albicans as the most susceptible strains. Moreover, the diameter of inhibition zone (DIZ) increased with increasing essential oil (EO) volume. Considerably superior antimicrobial activity was observed in the vapour phase. The DIZ resulting from the exposure to EO vapour was significantly larger than that from the same volume in the liquid phase. The DIZ varied from 22 to 90 mm for Candida strains. There is growing evidence that EO in vapour phase are effective antimicrobial systems and that they do have advantages over the use of oil in liquid phase. Our results imply that lemongrass oil could be useful for the development of novel types of natural preservatives for food control.     

Alginate/gelatin crosslinked system through Maillard reaction: preparation,characterization and biological properties

Maillard reaction (MR) was studied in aqueous model systems containing gelatin and sodium alginate, which were heat treated for different pH (7, 8, 9, 10 and 11) at three temperatures (70, 80 and 90 °C). Some indicators were used to evaluate this reaction:degree of crosslinking, release of gelatin, free amino groups and browning intensities. The results indicated that alginate/gelatin crosslinked by MR showed an increase of degree of crosslinking as the pH and temperatures were increasing while release of gelatin decreased. Furthermore, samples prepared at a high temperature exhibited stronger browning intensity owing to the formation of Maillard reaction products (MRPs). The obtained materials were analyzed by FTIR and XRD. The antioxidant ability by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and power reducing, as well as the anti-inflammatory activity were investigated.     

Synthesis of copolymer from 1,3,5‐trioxane and 1,3‐dioxolane catalyzed by Maghnite‐H+

Copolymers (polyoxymethylene) were prepared by cationic copolymerization of 1,3,5‐trioxane (TOX) with 1,3‐dioxolane (DOX) in the presence of Maghnite‐H⁺ (Mag‐H⁺) in solution. Maghnite is a Montmorillonite sheet silicate clay, with exchanged protons to produce Mag‐H⁺. Various techniques, including ¹H‐NMR, ¹³C‐NMR, FT‐IR spectroscopy, and Ubbelohde viscometer were used to elucidate structural characteristics properties of the resulting copolymers. The influence of the amount of catalyst, of dioxolane (DOX), temperature, solvent, and time of copolymerization on yield and on intrinsic viscosity of copolymers was studied. The yield of copolymerization depends on the amount of Mag‐H⁺ used and the reaction time. We also propose mechanisms involved in the synthesis of copolymer (polyoxymethylene). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Nonlinear speed estimation of a GPS-free UAV

In this article, the problem of robust state observer design for a class of unmanned aerial vehicles (UAVs) is addressed. A prototype four-rotors helicopter robot for indoors and outdoors applications is considered: the drone is not equipped with GPS related devices, so we describe a strategy to estimate its translational velocity vector based on acceleration, angles and angular speeds measurements only. Since the linearised system is non-observable at the equilibrium point, a nonlinear observability verification is performed for persistently exciting trajectories. A global exponential solution to this open problem is provided in the framework of adaptive observation theory when exact measurements are available. A modified observer is presented to enhance velocity estimation robustness in the realistic case of noisy measurements. The results are compared with a classical estimation strategy based on the extended Kalman filter to test the algorithm's performance.     

A comparative study of a direct and pulse electrodeposition method of TiO2 films and its effect on photoelectrocatalytic degradation of methyl orange dye

The present study reports the titanium dioxide (TiO2) films synthesized from TiCl3 precursor on ITO glass substrates using two electrochemical techniques, namely direct electro-deposition (DE) and pulse electro-deposition (PE). The synthesis potential during the time-on (Ton) period was fixed at ?1.5 V. However, the open-circuit potential was applied during the time-off (Toff) period. The effect of the technique of electro-deposition and Toff duration on the properties of TiO2 films and their photoelectron-catalytic activity were investigated. The obtained films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-VIS spectrometer, and photocurrent measurement respectively. It is found that the use of the PE technique at different Toff improves the properties of TiO2 films compared to the DE technique. The XRD patterns show the anatase phase with a marked preferential orientation along the (101) direction for all samples. From the SEM analysis, it is seen a significant change from big multigrain agglomerates at DE to a dense film structure and small multigrain agglomerates at different Toff. As the Toff decreases from 3 s to 1 s, the photocurrent response rises and reaches a high value of about 12 mA/cm2. Compared with DE, and under UV light the photocatalytic property of TiO2 film synthesis via PE has been improved in the degradation of methyl orange (MO). Finally, the films deposited at low Toff (Toff =1 s) show a faster degradation of MO.     

Study of the cooperativity at the glass transition temperature in PC/PMMA multilayered films: Influence of thickness reduction from macro- to nanoscale

In multilayered polymer films, the influence of thickness reduction on the glass transition temperature (T_g) and cooperatively rearranging region (CRR) size was investigated using temperature modulated differential scanning calorimetry (TMDSC). The materials used in this work are multilayered films comprising tens to thousands of alternating layers of two polymers, Bisphenol A Polycarbonate (PC) and polymethyl-methacrylate (PMMA) fabricated by layer multiplying coextrusion technique. The TMDSC measurements enable the calculation of the average values of CRR parameters at the dynamic glass transition temperature (T_g) using Donth’s method. The molecular mobility in each polymer is found to be altered in entirely different ways as the thickness of each component became thinner than 125 nm, whereby the polymers exist as two dimensional layers under those conditions. PC exhibits a drastic decrease in cooperativity volume at the glass transition while slight modifications are observed for PMMA. These observations are discussed in regard with the role of the large interface amount between the two different polymers and the evolution of the macromolecule conformations.     

Mineralogical Analysis of Sand Roses and Sand Dunes Samples from Two Regions of South Algeria

Silicon - In this work, it is found that the important minerals in sand dunes and sand roses samples from Anqousa in the south-east of Algeria in Ouargla region and from Charouin in the south-west...     

Antioxidant and gastroprotective actions of butanol fraction of Zingiber officinale against diclofenac sodium‐induced gastric damage in rats

This study was designed to investigate the antioxidant and antiulcer activities of flavonoid‐rich fractions of Zingiber officinale extract. The fractions, obtained by solvents of increasing polarities, were subjected to 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging activity. The fraction which possessed the highest antioxidant activity was used to assess gastroprotective action against diclofenac sodium induced gastric ulcer in rats. Chromatographic profiling was carried out using LC‐ESI‐MS analysis. The butanol fraction (BF) showed the strongest antioxidant potential and the results of the in vivo study revealed that BF at 100 mg/kg protected against gastric lesions. At the same dose, BF prevented diclofenac sodium‐induced increase in tumor necrosis factor alpha (TNF‐α) and malondialdehyde (MDA) levels, and depletion of catalase (CAT) activity as well as glutathione (GSH) and prostaglandin E2 (PGE2) contents. LC‐ESI‐MS analysis revealed the presence of 12 phenolic compounds. BF exerted antiulcer action which could be linked to the presence of phenolic compounds.

Practical applications

Zingiber officinale has been widely consumed as a spice and used in folk medicine for treatment of gastric disorders. This is the first report evaluating the pharmacological effects of the butanol extract of ginger for the prevention of gastric ulcer. The results showed that the extract affords better gastroprotective activity against diclofenac sodium‐induced gastric ulcer in rats by reducing oxidative stress. Information provided in this study will be beneficial for developing applications of ginger in food biotechnology as functional and nutraceutical ingredient.     

Preparation of Nano-TiO2/Diatomite Composites by Non-hydrolytic Sol–Gel Process and its Application in Photocatalytic Degradation of Crystal Violet

Silicon - The dispersion of anatase TiO2 on diatomic material was a prospective route to avoid agglomerates of these particles. In this work, the TiO2/diatomite composites were prepared using a...